Individual differences in second-language vowel learning

Abstract

Adults often have difficulty in acquiring non-native vowels especially when the
vowel inventories in first (L1) and second language (L2) are very different.
However, even when testing L2 groups with similar profiles, there are great
individual differences in the perception and production of non-native sounds.
Similarly, computer-based training studies of L2 sounds report that improvement
after training can range greatly across individuals. This thesis explores possible
sources of individual differences in Greek native speakers’ perception and
production of Southern British English vowels.
Study 1 examined the perceived relationship between English vowels (in /bVb/ and
/bVp/ contexts) and Greek vowels along with English vowel discrimination by the
same participants. Greek speakers were found to perceive English vowels via both
spectral and temporal assimilation to their L1 categories despite the fact that Greek
does not use duration in L1 vowel distinctions. Study 2 defined the endpoints for the
synthetic vowel continua to be used in Study 3 using a best exemplars experiment. In
study 3, Greek speakers from a homogenous population (in terms of L1 background,
age of L2 learning, amount and quality of L2 input) were tested on a large test
battery before and after receiving 5 sessions of high-variability perceptual training.
The test battery examined their perception of natural and synthetic vowels in L1
(Greek) and L2 (English) and their frequency discrimination ability (F2 only) as well
as their production of L2 vowels. Group results showed significant improvement in
the trainees’ perception of natural L2 vowels and their L2 vowel production.
However, large individual differences were evident both before and after training.
Vowel processing in L2 was found to relate to individual variability in vowel
processing in L1 and, importantly, to frequency discrimination acuity, a finding that
favours an auditory processing hypothesis for L1 and L2 speech perception of
vowels.